The present invention generally relates to a press installation and more particularly to a press installation arrangement for minimizing transfer distances for sheet metal parts to be transferred between individual presses of the press installation.
Reference is made to the below listed related U.S. applications:
(i) U.S application Ser. No. 380,508, filed July 17, 1989, now abandoned based on German Application No. P 39 05 068.8 filed in Germany on Feb. 18, 1989; and
(ii) U.S. application Ser. No. 413,607, filed Sept. 28, 1989, based on German Application No. P 39 05 073.4 filed in Germany on Feb. 18, 1989.
The working of sheet metal parts typically takes place in several working steps. Originally, individual presses, for example, so-called auto-body presses were used. When they were further developed into press trains, the working of the sheet metal parts first took place by a manual handling of the sheet-metal parts, and later by a partially mechanized and then by a fully automated conveying of the metal sheets.
The necessity for reducing investment and operating costs has led to a combining of working steps originally carried out on individual presses in press trains by utilizing compact, multistage multiframe transfer presses. Multiframe transfer presses meet the requirement of high flexibility, high output and short retooling times. For example, the eight working steps, which are required for the manufacturing of the sheet metal parts in automobile construction are distributed on one, two or three slides in the multiframe transfer presses.
As a result of the dimensions of the sheet metal parts, tool center distances of 2,500 mm and more are experienced, and the sheet metal parts and the devices for the transferring of the sheet metal parts in the working stages must be accelerated to a high speed in order to obtain high ejection rates in order to achieve large piece numbers for the transfer movements.
In German Patent Specification (DE-PS) 12 71 067 C, a press train is disclosed and in German Published, Examined Patent Application (DE-AS) 23 59 912 C2 a multiframe transfer press is disclosed. The disclosures of the above noted patents are discussed below.
The press train disclosed by (DE-PS) 12 71 067 C employs a multiple-action drawing press, which is operated continuously and is used as the head press, with a system for conveying sheet-metal parts through the press train which is controlled by the head press. In order to avoid turning devices between the head press and the press which follows and thus reduce the distances between the presses, the drawing press is equipped with a drawing slide operating in an upward direction and with a sheet holder slide operating in a downward direction.
The conveying system for the sheet-metal parts has a gripper rail system extending through the whole press train which can be moved along three axes for providing an opening and closing movement of the gripper rails, a lifting and lowering of a gripped work piece and a forward transfer and reverse movement of the gripper rails. Each press constitutes a separate machine. The use of gripper rails guided through the press train is useful only if the press slides of the individual presses also permit a synchronous transfer movement of the sheet metal parts. If the press train is to be operated in a fully synchronized manner, expensive synchronizing devices must be used for this purpose. Although the set-up of the individual presses has led to reduced space requirements, because of the elimination of the turning device and the resulting shorter distance between the presses, the low space requirement of multiframe transfer presses cannot be achieved. In addition, a relatively large press foundation is required, and the transfer step of the gripper rail system is also still relatively wide.
Moreover, the large mass of the conveying gripper rail system requires high driving forces at high acceleration values. Large-surface sheet metal parts as well as thin-walled sheet metal parts, i.e., all sheet metal parts which are unstable due to bending and the like, can be worked and transferred in the press train only to a limited extent, particularly if a high ejection rate (such as 16 parts per minute) is to be achieved. A tool change using sliding tables, for supporting tools, dies and the like which can be moved into and out of the presses, is not provided. Further, the linkage of rods for facilitating the movements of the gripper rail system along the three axes extends over the length of the press train, and the gripper rails interfere considerably with the changing operation of the tools of the slides.
(DE-AS) 23 59 912 CA discloses a transfer press having several working stations which follow one another. The transfer press is a multiframe transfer press having a headpiece, which is supported by frames, a press bed and slides, which can be lifted and lowered by a common drive. Tools or tool sets are assigned to the slides. In the area of the press frames, no-operation stages or so-called idle stages are provided in which intermediate depositing devices are arranged for receiving sheet metal parts. The drive of the two gripper rails along the three axes is taken from the main drive of the press or an auxiliary drive by means of cam control devices. Tools or tool sets and parts of the gripper rails can be exchanged using sliding tables which are moved into and out of the transfer press. The deforming and/or shearing forces differ in the individual working stages. However, the one-sided loading of the slides as well as the deflections of the slide, the table and the tool have a disadvantageous effect on the working and output capabilities of such a transfer press.
In order to avoid a breaking of the tool and the press, the working stages of each of the slides must be protected both individually and collectively. In the case of excessive pressure increases in the individual working stages and in the individual connecting rods, the transfer press must switch off, and therefore high expenditures are required for protecting the tools and the transfer press.
The tools or tool sets cannot be adjusted separately and must therefore first be adjusted to the working values. A change of the adjustment of one tool generally results in the change of all tools. As a result of the large center distance of the tools and thus of the large transfer movement of the sheet metal parts per slide stroke, the masses of the transfer rails must be accelerated and as a result, the output of the transfer press is low. High acceleration values and, in this case, the accelerations of large masses, result in vibrations in all parts of the press. The precision of the transfer and of the deforming of the workpieces is impaired. Also in the case of transfer presses, the transfer movement of the sheet metal parts corresponds to the center distance of the tools.
Accordingly, it is an object of the present invention, particularly in view of the increasingly large surfaces of the sheet metal parts to be transferred which are thin-walled and are therefore unstable, to significantly shorten the length of the transfer movement of the sheet metal parts per slide stroke, in order to thus reduce acceleration values.
In addition, it is a further object of the present invention to reduce the distance between the guides of each of the slides in order to improve the guiding ratio of the distance of the guides with respect to one another to the length of the guides and thus effect an improvement of the lateral guiding of each of the slides.
In addition, yet another object of the present invention is to assure that the elements of the device for the transfer of the sheet metal parts are lifted sufficiently far during tool changing times so that they do not impair the changing operation.
These and other objects are achieved by a hybbrid press installation which uses advantageous features of the press train and multiframe press discussed above.
In contrast to a press train and a multiframe transfer press, it is an advantage that the hybrid press installation, according to preferred embodiments of the present invention, has several presses, a single working stage being performed by each press so that a significantly smaller overall installation surface is required. On the whole, the conveying paths of the sheet metal parts are also reduced considerably. Further, the number of strokes and the output of the press installation may be increased. The press installation forms a system which is complete in itself and the working stages do not mutually influence one another as a result of the deforming operations. Moreover, the central control of all systems, such as the pressure consuming devices, the sequence of movements, the tool change and the like is advantageous in this case.
In comparison to a multiframe transfer press, the elimination of the mutual influencing of the working stages is advantageous as is the ability to protect each tool and thus of each slide by means of separate overload protection devices. Thus an improved overload protection is achieved. Each tool can be adjusted separately, and the reworking of these tools is significantly facilitated. The accessibility of the slides, of the tool tighteners, of the tools and of the part-receiving elements is also improved.
Additional advantages are the smaller masses and the lower space requirement of the sliding tables, the quieter conveying of the sheet metal parts, the active integration of intermediate depositing devices into the workpiece passage, including the provision to an inclined position for the arriving sheet metal parts and the providing of a new inclined position, and an easier construction of the press installation with an increased number of installation areas. Additionally, the static and dynamic loads on the foundation are reduced and more evenly distributed.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.